The present invention relates to binder compositions and methods for curing such binder compositions. The binder compositions of the present invention are especially useful as molding compositions such as refractories, abrasive articles, and molding shapes such as foundry cores and molds. The binder compositions are capable of hardening at ambient temperatures.
Various binder systems now used including binders for molding compositions employ inorganic substances as the major components. However, prior art binders from inorganic substances have suffered from one or more deficiencies. Typical of the deficiencies exhibited by prior art inorganic binders including the silicates suggested for molding shapes such as cores and molds have been poor collapsibility of the shape and poor removal or "shake out" of the molding shape from the metal casting.
Also, many of the suggested inorganic binders exhibit inadequate bonding strength properties and/or undesirable cure characteristics.
Moreover, various prior art inorganic binders such as the silicates provide molding shapes and particularly ambient temperature cured shapes which possess poor scratch resistance at strip; and accordingly, such shapes require at least a few additional hours after strip time has been achieved to develop adequate scratch resistance. In view of the poor scratch resistance at strip, such shapes cannot be readily handled at strip because of the danger of damage to the shape. Moreover, the sag resistance at strip of the shapes prepared from various prior art binders is not good.
Another problem which may exist is the degradation of physical properties such as tensile strength and hardness of molded articles after storage for only a few hours.
It is therefore an object of the present invention to provide inorganic binder systems which possess acceptable strength characteristics. It is another object of the present invention to provide inorganic binder systems wherein the cure characteristics can be manipulated within certain limits.
It is a further object of the present invention to provide inorganic binder systems for molding shapes which possess relatively good collapsibility and shake out properties as compared to various other suggested inorganic binders.
It is another object of the present invention to provide molding shapes employing inorganic binders which possess good scratch and sag resistance at strip. Likewise, it is an object of the present invention to provide molding shapes from inorganic binder systems which can be readily and easily handled at strip.
It is also an object of the present invention to provide molded articles which demonstrate improved resistance to deterioration of physical properties such as tensile strength and hardness due to storage.